Семинар 254 – 23 ноября 2023 г.


Иван Герасимов

Презентация

2311.08160 The spatially resolved star formation history of the dwarf spiral galaxy NGC 5474

G. Bortolini, M. Cignoni, E. Sacchi, M. Tosi, F. Annibali, R. Pascale, M. Bellazzini, D. Calzetti, A. Adamo, Daniel. A. Dale, M. Fumagalli, John. S. Gallagher, K. Grasha, Kelsey E. Johnson, Sean. T. Linden, M. Messa, G. Östlin, E. Sabbi, A. Wofford

Published 2023-11-14, 18 pages, 12 figures, accepted for publication in Monthly Notices of the Royal Astronomical Society

We study the resolved stellar populations and derive the star formationhistory of NGC 5474, a peculiar star-forming dwarf galaxy at a distance of$\sim 7$ Mpc, using Hubble Space Telescope Advanced Camera for Surveys datafrom the Legacy Extragalactic UV Survey (LEGUS) program. We apply an improvedcolour-magnitude diagram fitting technique based on the code SFERA and use thelatest PARSEC-COLIBRI stellar models. Our results are the following. Theoff-centre bulge-like structure, suggested to constitute the bulge of thegalaxy, is dominated by star formation (SF) activity initiated $14$ Gyr ago andlasted at least up to $1$ Gyr ago. Nevertheless, this component shows clearevidence of prolonged SF activity (lasting until $\sim 10$ Myr ago). Weestimate the total stellar mass of the bulge-like structure to be $(5.0 \pm0.3) \times 10^{8}$ \MSUN. Such a mass is consistent with published suggestionsthat this structure is in fact an independent system orbiting around and notwithin NGC 5474's disc. The stellar over-density located to the South-West ofthe bulge-like structure shows a significant SF event older than $1$ Gyr, whileit is characterised by two recent peaks of SF, around $\sim10$ and $\sim100$Myr ago. In the last Gyr, the behavior of the stellar disc is consistent withwhat is known in the literature as `gasping'. The synchronised burst at $10-35$Myr in all components might hint to the recent gravitational interactionbetween the stellar bulge-like structure and the disc of NGC 5474.